The errata sheet already has an error flagged for this page but I noticed something else:

In the 'Program 8.4 Rectangle.m Added methods' code display where it shows the methods added to the 'Rectangle.m' file, there are a few things that are confusing/wrong:

1. It shows #import "XYPoint.h" at the beginning of the file; it should be #import "Rectangle.h". The full 'Rectangle.m' code listing that appears on the next page has it correctly.

2. This code listing is just the added methods but it is formatted suggesting that this is the complete *.m file. There is '@end' there at the end. It seems there should be some ellipses (...) at the beginning and end to be consistent with the fact that the info here are just code snippets and not the complete file.